1. Field of the Invention
The present invention relates to a two-fluid cleaning jet nozzle and cleaning equipment comprising the same. More particularly, it relates to a two-fluid cleaning jet nozzle and cleaning equipment for removing contaminants adhering to the surface of a substrate such as a semiconductor wafer, a liquid crystal substrate, a disk substrate or a photomask. It also relates to a method of fabricating a semiconductor device.
2. Description of the Prior Art
In general, it is known that various contaminants adhere onto the surface of a semiconductor wafer in a semiconductor fabrication process. When an insulator film or a metal film is formed on a semiconductor wafer by CVD (chemical vapor deposition) or sputtering, for example, particulate contaminants adhere to the surface of the formed film. Further, etching residues (resist residues) or metal contaminants adhere after pattern formation by dry etching. As a method of removing such contaminants, Japanese Patent Laying-Open No. 10-156229 (1998) proposes a method of injecting droplets from a two-fluid cleaning jet nozzle.
FIG. 9 is a sectional view of a conventional two-fluid cleaning jet nozzle 51. This two-fluid cleaning jet nozzle 51 injects droplets formed by mixing a gas and a liquid with each other in the air and collides the same against the surface of an unclean substance thereby cleaning the substance. In the two-fluid cleaning jet nozzle 51, a pressurized gas and a pressurized liquid are supplied through a gas inlet 2 and a liquid inlet 3 respectively, to be mixed with each other in a mixing part 21 shown in FIG. 9. Thus, the liquid is converted into droplets floating in the gas. The gas is supplied through the gas inlet 2 under a high pressure, to form a fast stream in a straight pipe 22. The droplets formed in the mixing part 21 are accelerated by the stream of the gas in the straight pipe 22. The accelerated droplets are reduced in particle diameter. Thus, the droplets are injected through an outlet 4 of the straight pipe 22.
FIG. 10 is a schematic sectional view of conventional cleaning equipment comprising the two-fluid cleaning jet nozzle 51. This cleaning equipment is now described with reference to a semiconductor wafer 10 to be cleaned. The cleaning equipment comprises a stage 11 for holding the semiconductor wafer 10, a motor 12 for rotating the stage 11, the two-fluid cleaning jet nozzle 51 directed to a surface, to be cleaned, of the semiconductor wafer 10 set on the stage 11, and a cleaning cup 52 for preventing the droplets from scattering in cleaning. The cleaning cup 52 is provided with downwardly directed discharge ports 53. Operations of the cleaning equipment are now described. The semiconductor wafer 10 is set on and fixed to the stage 11, which in turn is rotated by the motor 12 at a prescribed rotational frequency. The gas and the liquid are supplied into the two-fluid cleaning jet nozzle 51, which in turn injects the droplets and the gas from the forward end thereof. Consequently, the droplets collide against contaminants adhering to the surface of the semiconductor wafer 10 to remove the contaminants. The contaminants removed from the surface of the semiconductor wafer 10 and most of the droplets and the gas injected from the two-fluid cleaning jet nozzle 51 flow toward the outer periphery of the semiconductor wafer 10, to be discharged through the discharge ports 53.
While the contaminants and most of the liquid and the gas are discharged through the discharge ports 53, the liquid is partially converted to a mist and the contaminants originally adhering to the surface of the semiconductor wafer 10 rise up in the cleaning cup 52 along with particles originally contained in the gas, to disadvantageously re-adhere to the surface of the semiconductor wafer 10 in a certain probability.
In the conventional two-fluid cleaning jet nozzle 51 or the cleaning equipment comprising the same, most part of the injected gas is directly sprayed to the surface (hereinafter referred to as xe2x80x9ccleaned surfacexe2x80x9d) of the substance to be cleaned, and hence the cleaned surface is dried to readily allow adhesion of particles. When the removed contaminants rise up in the cleaning cup 52 as hereinabove described, the particles originally contained in the gas frequently collide against the cleaned surface, to disadvantageously adhere to the cleaned surface. In particular, a fine pattern formed on the surface of a semiconductor substrate or the like may be damaged due to collision with such particles contained in the gas.
Further, it is difficult to quickly discharge the liquid and the gas through the discharge ports 53 connected under the cleaned substance. Thus, fine droplets partially converted to a mist, temporarily removed contaminants and particles contained in the gas readily rise up in the cleaning cup 52, to readily adhere to the cleaned substance.
An object of the present invention is to provide a two-fluid cleaning jet nozzle and cleaning equipment capable of suppressing re-adhesion of contaminants to a cleaned surface, adhesion of particles and damage of a fine pattern resulting from collision with particles.
In order to attain the aforementioned object, a two-fluid cleaning jet nozzle according to an aspect of the present invention comprises a mixing part mixing two types of externally supplied fluids with each other for preparing a fluid mixture, a straight pipe linearly and tubularly formed along a prescribed accelerating direction toward the surface of a cleaned substance for accelerating the aforementioned fluid mixture received from the aforementioned mixing part along the aforementioned accelerating direction and a bent part connected to an outlet of the aforementioned straight pipe, while the aforementioned bent part has an inner surface communicating with the inner surface of the aforementioned straight pipe and this inner surface of the aforementioned bent part defines a convexly bent curved surface to spread outward with respect to a space receiving the aforementioned fluid mixture injected from the aforementioned straight pipe. According to this structure, droplets injected from the outlet of the straight pipe can linearly advance as such to collide against a cleaned surface and remove contaminants, while a gas injected from the outlet of the straight pipe flows along the inner surface of the bent part due to a Coanda effect, not to directly collide against the cleaned surface. Particles originally contained in the gas also move along the stream of the gas, to be prevented from colliding against the cleaned surface.
In order to attain the aforementioned object, a two-fluid cleaning jet nozzle according to another aspect of the present invention comprises a mixing part mixing two types of externally supplied fluids with each other for preparing a fluid mixture, a straight pipe linearly and tubularly formed along a prescribed accelerating direction for accelerating the aforementioned fluid mixture received from the aforementioned mixing part along the aforementioned accelerating direction and a gas shield arranged apart from an outlet of the aforementioned bent part in a direction substantially perpendicular to the aforementioned accelerating direction, and the aforementioned gas shield has an opening on a position intersecting with a line formed by extending the center line of the aforementioned straight pipe. According to this structure, most part of a gas collides against the gas shield, to be hardly sprayed to a cleaned surface. On the other hand, droplets rectilinearly advance as such due to the law of inertia to pass through the opening and collide against the cleaned surface, whereby only the droplets can be more reliably collided against the cleaned surface.
In order to attain the aforementioned object, cleaning equipment according to still another aspect of the present invention comprises a stage for receiving a cleaned substance thereon, a two-fluid cleaning jet nozzle arranged toward a position of the aforementioned stage for receiving the aforementioned cleaned substance, walls enclosing the aforementioned stage and a discharge port arranged on a position intersecting with a plane formed by extending a cleaned surface of the aforementioned cleaned substance set on the aforementioned stage. According to this structure, the discharge port is arranged on extension of a stream of a gas formed toward the outer periphery of the cleaned surface, whereby the gas can be smoothly discharged from the discharge port.
In order to attain the aforementioned object, cleaning equipment according to a further aspect of the present invention comprises a stage for receiving a cleaned substance thereon and a two-fluid cleaning jet nozzle arranged toward a position of the aforementioned stage for receiving the aforementioned cleaned substance, while the aforementioned two-fluid cleaning jet nozzle includes a mixing part mixing two types of externally supplied fluids with each other for preparing a fluid mixture, a straight pipe linearly and tubularly formed along a prescribed accelerating direction toward the surface of a cleaned substance for accelerating the aforementioned fluid mixture received from the aforementioned mixing part along the aforementioned accelerating direction and a bent part connected to an outlet of the aforementioned straight pipe, the aforementioned bent part has an inner surface communicating with the inner surface of the aforementioned straight pipe, this inner surface of the aforementioned bent part defines a convexly vent curved surface to spread outward with respect to a space receiving the fluid mixture injected from the aforementioned straight pipe, and an end of the aforementioned bent part is present in a plane substantially parallel to a cleaned surface of the aforementioned cleaned substance set on the aforementioned stage. According to this structure, a gas flowing along the inner surface of the bent part is discharged from the end of the bent part as a stream along the surface of the cleaned substance, whereby the gas is more smoothly discharged and can be prevented from rising or the like.
In order to attain the aforementioned object, cleaning equipment according to a further aspect of the present invention comprises a stage for receiving a cleaned substance thereon and a two-fluid cleaning jet nozzle arranged toward a position of the aforementioned stage for receiving the aforementioned cleaned substance, while the aforementioned two-fluid cleaning jet nozzle includes a mixing part mixing two types of externally supplied fluids with each other for preparing a fluid mixture, a straight pipe linearly and tubularly formed along a prescribed accelerating direction for accelerating the aforementioned fluid mixture received from the aforementioned mixing part along the aforementioned accelerating direction and a gas shield arranged apart from an outlet of the aforementioned bent part in a direction substantially perpendicular to the aforementioned accelerating direction, and the aforementioned gas shield has an opening on a position intersecting with a line formed by extending the center line of the aforementioned straight pipe. According to this structure, most part of a gas collides against the gas shield, to be hardly sprayed to a cleaned surface. On the other hand, droplets rectilinearly advance as such due to the law of inertia to pass through the opening and collide against the cleaned surface, whereby only the droplets can be more reliably collided against the cleaned surface for cleaning the cleaned surface.
In order to attain the aforementioned object, a method of fabricating a semiconductor device according to a further aspect of the present invention employs the two-fluid cleaning jet nozzle according to any of the aforementioned aspects. According to this method, the surface of a cleaned substance can be prevented from damage as well as re-adhesion of temporarily removed contaminants and adhesion of particles contained in a gas for enabling excellent cleaning, whereby a semiconductor device can be efficiently fabricated with a high yield.
In order to attain the aforementioned object, a method of fabricating a semiconductor device according to a further aspect of the present invention employs the cleaning equipment according to any of the aforementioned aspects. According to this method, the surface of a cleaned substance can be prevented from damage as well as re-adhesion of temporarily removed contaminants and adhesion of particles contained in a gas-for enabling excellent cleaning, whereby a semiconductor device can be efficiently fabricated with a high yield.